The following description and examples are not admitted to be prior art by their mention in this Background section.
In order to enhance the yield and reliability of the semiconductor devices such as integrated circuits (ICs) and memory devices, examining the defects on the patterned wafer for the avoidance of them has been significant. The physical defects, such as foreign particles, scratch defects, residual defects, bridging defects and so on, cause the devices to fail electrically, for example, the short or open circuit. Furthermore, since deep sub-micrometer node devices are developed, new and more complicated manufacturing structures such as a dual damascene structure and a fin-shaped field effect transistor (FinFET) structure are utilized in the semiconductor devices. Therefore, new types of defects including latent defects, for instance, chemical mechanical polishing (CMP) scores, under-layer leakage, under-etch, missing, voids, voltage contrast (VC) defects, and non-virtual defects (NVDs) occur during the manufacturing phase. Besides, while the less than 20 nm manufacturing process is on line, it has been a big challenge for the observation of nano-size semiconductor devices. It is consequence that the optical inspection apparatus has been stretched to the limit of its capability at the inspection of these defects and tiny devices. Herein, the issue is effectively addressed by a charged particle beam apparatus, for example, an electron beam tool based on a scanning electron microscope (SEM), and the semiconductor manufacturing and the yield enhancement can be optimized by the apparatus.
However, in terms of examination throughput, the charged particle beam apparatus remains much slower than the optical one. To fill the gap, the industry has presented a two-stage defect examination that includes a defect-inspection apparatus rapidly finding at what positions on the wafer defects are and a defect-reviewing apparatus being used to analyze the detected defects by the defect-inspection apparatus. In the defect-inspection apparatus, because of its rapidness being important, a large beam current is to be acquired and to be used with LFOV scan. In the defect-reviewing apparatus, because of its resolution being high for analyzing defects, a small beam current is used to acquire a defect image at high resolution. To sum up, in operation of detecting defects on the wafer, a defect map is rapidly acquired by the defect-inspection apparatus at first, and then the defect-reviewing apparatus analyzes defects and identifies killer defects according to the defect map, which improves the throughput and saves the cost.
Thus, there is an increasing need for high-resolution and/or high-throughput charged particle beam apparatuses such as high-resolution and/or high-throughput SEMs in manufacture of the advanced semiconductor devices. Examples of such apparatuses are illustrated in U.S. Pat. No. 4,330,709, which discloses a SEM has two magnetic deflectors inside objective lens and the deflectors are spaced apart the objective lens by a ferrite to increase the response time. Additional examples of such apparatuses are illustrated in U.S. Pat. No. 6,380,546, which discloses a SEM focusing system that has a beam guiding electrode and two magnetic deflectors in an objective lens. One of the two magnetic deflectors is arranged in the focusing field of the objective lens and the other is downstream the former. Such the arrangement decreases the chromatic aberration of focusing and deflection to obtain high resolution image. Additional examples of such apparatus are illustrated in U.S. Pat. No. 4,831,266, U.S. Pat. No. 4,926,054, U.S. Pat. No. 5,780,859, U.S. Pat. No. 6,194,729, U.S. Pat. No. 6,498,345 and U.S. Pat. No. 6,590,210, which disclose a SEM objective lens system that has a beam guiding electrode passing through it and a retarding lens to decelerate and focus an electron beam at low energies for maintaining high-resolution. The beam guiding electrode is used to direct and accelerate the electron beam onto a specimen and then secondary electrons (SE) and/or back-scattered electrons (BSE) from the specimen are accelerated by the retarding lens for enhancing the detection performance of a detector. However, these prior arts do not provide with the throughput improvement, and in some cases of hidden defects, for example VC defects, can't be observed by these prior arts apparatuses. Additional examples of such apparatuses are illustrated in U.S. Pat. No. 6,392,231, which discloses a swing objective retarding immersion lens (SORIL) SEM to enhance the throughput of prior arts apparatuses by a method of LFOV scan. However, the very high voltage is needed to accelerate the charged particle beam resulting in the arcing problem.
Accordingly, the prevent invention develops a charged particle beam apparatus for improving the throughput of semiconductor devices. The apparatus is used to find the defect position, detecting latent defects, and especially defects positioned under the surface layer.